refactor(application): migrate all queries to Stream-based API

- Replace byte[] and Base64String with required Stream PdfStream
- Simplify validators: remove XOR/Base64 validation, only check NotNull
- Affected queries: ValidatePdfQuery, ValidatePdfAQuery, CheckPdfAttachmentsQuery, ExtractSwissQrCodeQuery
- Memory efficiency: direct stream usage, no intermediate byte[] copies

DocumentOperator.Application/ValidatePdf/Queries/ValidatePdfQuery.cs

@@ -6,19 +6,14 @@ using MediatR;
 namespace DocumentOperator.Application.ValidatePdf.Queries;
 
 /// <summary>
-/// Query for PDF validation (supports both byte array and Base64 input)
+/// Query for PDF validation (Stream-based)
 /// </summary>
 public record ValidatePdfQuery : IRequest<PdfValidationResult>
 {
     /// <summary>
-    /// PDF as byte array (direct upload)
+    /// PDF as stream (caller is responsible for disposal)
     /// </summary>
-    public byte[]? PdfBytes { get; init; }
-
-    /// <summary>
-    /// PDF as Base64 string (API clients)
-    /// </summary>
-    public string? Base64Pdf { get; init; }
+    public required Stream PdfStream { get; init; }
 }
 
 /// <summary>
@@ -33,14 +28,8 @@ public class ValidatePdfQueryHandler(IPdfProcessor PdfProcessor, IMapper Mapper)
     /// </summary>
     public async Task<PdfValidationResult> Handle(ValidatePdfQuery request, CancellationToken cancellationToken)
     {
-        // Use byte[] if available, otherwise convert Base64
-        byte[] pdfBytes = request.PdfBytes ?? Convert.FromBase64String(request.Base64Pdf!);
-
-        // Convert to stream for IPdfProcessor (using MemoryStream)
-        using var pdfStream = new MemoryStream(pdfBytes);
-
-        // Call DevExpress service (exceptions propagate naturally)
-        var metadata = await PdfProcessor.ValidateAsync(pdfStream);
+        // Call DevExpress service directly with stream (exceptions propagate naturally)
+        var metadata = await PdfProcessor.ValidateAsync(request.PdfStream);
 
         // Map DTO to response DTO using AutoMapper
         return Mapper.Map<PdfValidationResult>(metadata);